单项选择题

This passage deals mainly with ______.

A．the gravitational pull of the Earth and the moon
B．the factors involved in firing a rocket into the outer-space
C．the gravitational fields of the Earth and the moon
D．the speed and direction of a rocket traveling in the outer-space

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热门试题

单项选择题

According to the passage, the most difficult task of fining a rocket is ______.

A．to get the rocket into the space
B．to calculate the rocket's velocity of escape
C．to guide the rocket after it leaves the Earth's surface
D．to identify the gravitational fields of the Earth and the moon

单项选择题

In the author's opinion, all the following are to blame for crime EXCEPT ______.

A．society
B．the criminals themselves
C．the suspension of life sentence
D．the defender's role